Changes in ultraviolet radiation in the 1990s: Spectral measurements from Reading, England

Abstract

Spectral, ultraviolet irradiance measurements have been made since 1990 at Reading (England). Ancillary measurements using a photodiode show that UV measurements are frequently affected by clouds. Consequently, it is not practical to simply use irradiance measurements to study possible ozone‐related changes in UV‐B over the timescale of the measurements. However, taking ratios of irradiances in bands covering UV‐B and UV‐A wavelengths can be used to reduce the cloud influence on measurements. Using these ratios and ozone vertical column measurements, the anticorrelation between ozone and UV‐B irradiances measured at the ground is demonstrated. These data also show that between 1993 and 1997, UV‐B at Reading has increased by 4.3%, compared to a decrease in ozone of 5.9%. The UV‐B increase is not a statistically significant trend, however, and serves only as an indication of the changes observed.